The java.lang.String class provides a lot of methods to work on string. By the help of these methods, we can perform operations on string such as trimming, concatenating, converting, comparing, replacing strings etc.
Java String is a powerful concept because everything is treated as a string if you submit any form in window based, web based or mobile application.
Let's see the important methods of String class.
The java string toUpperCase() method converts this string into uppercase letter.
String s="Sachin"; System.out.println(s.toUpperCase());//SACHIN System.out.println(s);//Sachin(no change in original)
The java string toLowerCase() method converts this string into lowercase letter.
String s="Sachin"; System.out.println(s.toLowerCase());//sachin System.out.println(s);//Sachin(no change in original)
The string trim() method eliminates white spaces before and after string.
String s=" Sachin "; System.out.println(s);// Sachin System.out.println(s.trim());//Sachin
String s="Sachin"; System.out.println(s.startsWith("Sa"));//true
String s="Sachin"; System.out.println(s.endsWith("n"));//true
The string charAt() method returns a character at specified index.
String s="Sachin"; System.out.println(s.charAt(0));//S System.out.println(s.charAt(3));//h
The string length() method returns length of the string.
String s="Sachin"; System.out.println(s.length());//6
A pool of strings, initially empty, is maintained privately by the class String.
When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned.
String s=new String("Sachin"); String s2=s.intern(); System.out.println(s2);//Sachin
The string valueOf() method coverts given type such as int, long, float, double, boolean, char and char array into string.
int a=10; String s=String.valueOf(a); System.out.println(s+10);
The string replace() method replaces all occurrence of first sequence of character with second sequence of character.
String s1="Java is a programming language. Java is a platform. Java is an Island."; String replaceString=s1.replace("Java","Kava");//replaces all occurrences of "Java" to "Kava" System.out.println(replaceString);